聚(St-BA)/SiO_2复合微球的制备及其乳胶膜性能研究

利用苯乙烯(St)和丙烯酸丁酯(BA)在纳米SiO2水分散体系中进行细乳液聚合,制备了成膜型聚(St-BA)/SiO2复合微球。研究了单体组成、SiO2用量和1-乙烯基咪唑(1-VID)用量对复合微球粒径的影响,采用动态光散射粒度分布仪(PCS)、透射电镜(TEM)、扫描探针显微镜(AFM)及DSC对复合微球及乳胶膜进行了表征。结果表明:制备得到的聚(St-BA)/SiO2复合微球具有草莓型结构,二氧化硅于表面富集,其平均粒径在192~327nm之间。对所得乳胶膜的研究发现,纳米SiO2粒子均匀分散在复合乳胶膜中,有机相和无机相达到纳米级复合,且该复合乳胶膜具有快速吸水和快速干燥的特性。     

细乳液聚合制备磁性复合微球研究进展

介绍了细乳液聚合的特点、细乳液聚合制备磁性复合微球的一般步骤;从制备影响因素角度,对近年来国内外细乳液聚合制备磁性复合微球的研究进行了综述。磁性复合微球主要采用正相细乳液聚合,影响微球制备的主要因素有乳化剂类型和用量、磁性纳米粒子表面修饰、超声分散、助稳定剂类型、交联剂引发剂和磁流体用量等。今后,细乳液聚合制备磁性复合微球的研究仍将关注提高复合微球性能(高磁响应性能、粒子大小可控且均匀、具有表面功能基团)及产率(磁性粒子包覆率)等方面。     

细乳液聚合制备二氧化钛/聚苯乙烯复合微球及其形貌分析

采用细乳液聚合法,以γ-甲基丙烯酰氧基丙基三甲基硅烷改性的TiO2粒子为核,制备了核壳结构的TiO2/聚苯乙烯(PS)复合微球。研究了超声细乳化时间、乳化剂十二烷基硫酸钠(SDS)的浓度、TiO2用量对细乳液粒径及其分布的影响。通过纳米粒度与Zeta电位分析仪、红外光谱、透射电镜等分析手段对产物进行了表征。结果表明,随着超声细乳化时间的增加,初始液滴的粒径变小。聚合后的乳胶粒粒径随着SDS浓度的增大而减小;TiO2用量不足导致乳胶粒粒径分布变宽,且出现双峰;制备所得的TiO2/PS复合微球粒度分布较为均匀,平均直径为176.5 nm,球形规整度较好。     

微乳液聚合和细乳液聚合

分别从微乳、细乳体系的形成,聚合机理及聚合特点等方断对两者进行了比较,并对各自的应用前景进行了展望。     

细乳液聚合法制备疏水性纳米二氧化硅-丙烯酸酯杂化乳液

采用细乳液聚合法制备了疏水性纳米二氧化硅-丙烯酸酯杂化乳液,研究了杂化乳液薄膜的应力-应变性能,并通过透射电子显微镜、X射线光电子能谱、扫描电子显微镜及凝胶渗透色谱对杂化乳液进行了表征.结果表明:杂化乳液薄膜的拉伸强度、扯断伸长率明显优于纯丙烯酸酯乳液薄膜;在杂化乳液中,二氧化硅被丙烯酸酯包裹,两相的相容性很好;杂化乳液的相对分子质量及其分布基本不随着疏水性二氧化硅用量的增加而变化,与纯丙烯酸酯乳液相当.     

PMMA/SiO2复合微球在常规乳液体系中的制备及其形态研究

以4-乙烯基吡啶(4-VP)为辅助单体,分别使用十二烷基硫酸钠(SDS)和OP-40(CA897)作乳化剂,在SiO2存在下用常规乳液聚合合成了PMMA/SiO2复合微球.在阴离子乳化剂体系中,通过改变聚合物乳胶粒大小可以得到不同形态的复合微球,在非离子乳化剂体系中,可以得到草莓型或核-壳形态的SiO2/PMMA复合微球,取决于单体滴加速度、乳化剂的浓度和单体/SiO2比.复合微球的形态通过透射电镜及扫描电镜进行表征.     

单分散PSt/SiO_2杂化材料微球的制备及表征

以硅酸乙酯和丙烯酸反应制备了硅酸乙酯-丙烯酸单体,再将其和苯乙烯通过无皂乳液法共聚制备了单分散PSt/SiO2杂化材料微球。用FTIR、SEM、EDS、TG-DSC等对杂化材料微球进行了表征。结果表明有机组分和无机组分间以Si-O-C键相连接成交联结构,杂化材料只有一个玻璃化转变温度120℃,杂化材料微球粒径均一、大小约为300nm,单分散性的杂化材料微球乳液在室温下蒸发很容易自组装成有序的结构。     

细乳液聚合法制备含结晶紫微球乳液的研究

本研究采用过硫酸钾为水溶性引发剂,利用细乳液聚合来制备含结晶紫油溶性染料功能化乳液。反应完成后,用称量法测定其转化率,用紫外-可见光吸收光谱进行表征,用动态光散射测试粒径大小,并通过扫描电镜观察了纳米粒子形貌,用TG表征其热稳定性能,最终得到了制备含结晶紫纳米聚合物微球彩色乳液的一般方法。     

改进的无皂乳液聚合法制备单分散的聚苯乙烯微球

采用加入微量乳化剂(其浓度低于临界胶束浓度)的无皂乳液聚合法成功制备了单分散的聚苯乙烯(PS)微球。考察了聚合反应过程中的乳化剂浓度、单体浓度、引发剂浓度和离子强度等因素对PS微球粒径、单分散性和单体转化率的影响。用激光粒度仪和扫描电子显微镜对微球粒径、单分散性指数和表面形貌进行了表征。结果表明,改进的无皂乳液聚合法制备的PS微球具有粒径较小(100~350 nm)、单分散性好、转化率高等优点。     

界面细乳液聚合制备有机-无机杂化纳米胶囊

将甲基丙烯酸3-三甲氧基硅丙酯(MPS)引入以小分子烃为模板的苯乙烯细乳液聚合中,制备有机-无机杂化纳米胶囊。MPS由于其水解产物的亲水性及能够水解-缩合反应的特性使得MPS能够同时起界面聚合诱导剂和自由基锚定剂的作用,制备有机-无机杂化纳米胶囊,但囊化率不高。为了强化MPS的诱导和锚定作用,向体系中进一步加入N-异丙基丙烯酰胺(NIPAM)、二乙烯基苯(DVB),可以得到囊化率更高的产品。详细讨论了NIPAM、DVB用量对有机-无机杂化纳米胶囊形态的影响。乳化剂用量以及小分子烃模板含量也是影响胶囊形态的重要因素。     

微滴乳液聚合制备PDMS/SiO2纳米复合材料

采用超声分散的方法,以少量八甲基环四硅氧烷(D₄)对硅溶胶粒子进行表面接枝改性。然后在改性硅溶胶存在下,以十二烷基苯磺酸(DBSA)为乳化剂兼催化剂进行D₄的微滴乳液聚合,得到聚硅氧烷(PDMS)/二氧化硅(SiO₂)纳米复合乳液。采用FTIR、TGA、纳米粒度仪、TEM和拉力机分别对样品进行了表征。结果表明:采用超声分散的方法,能够有效地实现硅溶胶粒子的表面改性。通过微滴乳液聚合得到的复合乳胶粒是聚合物包覆二氧化硅粒子的核壳结构形态。SiO₂的引入提高了有机硅复合膜力学性能,增强了热稳定性。     

Preparation of acrylate polymer/silica nanocomposite particles with high silica encapsulation efficiency via miniemulsion polymerization

Acrylate polymer/silica nanocomposite particles were prepared through miniemulsion polymerization by using methyl methacrylate/butyl acrylate mixture containing the well-dispersed nano-sized silica particles coupling treated with 3-(trimethoxysilyl)propyl methacrylate (MPS). The encapsulation efficiency of silica particles was determined through the elution and hydrofluoride acid etching experiments, and the size distribution and the morphology of the composite latex particles were characterized by dynamic light scattering and transmission electron microscopy. The coupling treatment of silica with MPS can improve the encapsulation efficiency of silica and the degree of grafting of polymer onto silica. When 0.10 g MPS/g silica was used to modify silica, the encapsulation efficiency of silica was greater than 95%, and the degree of grafting of acrylate polymer onto silica was about 60%. Although the average size and the size distribution index of the composite latex particles increased as the weight fraction of silica increased, the stable latex containing the ‘guava-like’ composite particles was obtained. The grafting of polymer onto silica particles improved the dispersion of silica particles in the solvents for acrylate polymer and in the polymer matrix.     

Synthesis of structured nanoparticles of styrene/butadiene block copolymers via RAFT seeded emulsion polymerization

The structured nanoparticles of styrene (St) and butadiene (Bd) block copolymers were prepared by RAFT seeded emulsion polymerization of butadiene. It was confirmed that the block copolymers of PSt-b-P(St-co-Bd) was formed with controlled molecular weight and rather low PDI at low composition of the P(St-co-Bd) segment. With more incorporation of butadiene, the branching reaction of polybutadiene became obvious, leading to higher PDI and positive deviation of M_n from the theoretical predication. At the gel point, the composition of the P(St-co-Bd) segment was estimated to be 0.72. After this, the gel fraction increased quickly. The morphology of structured nanoparticles could be largely tuned simply by the copolymer composition. With the composition of the P(St-co-Bd) segment increased from 0.37 to 0.92, the morphology within the structured particles changed from the polybutadiene domains-in-polystyrene matrix, perforated concentric-spherical layer, concentric-spherical multi-layers, bi-continuous, to broken layers of polystyrene in polybutadiene matrix. It was found that the morphology of the block copolymer within nanoparticles was dependent on d/L values, which was in excellent agreement with the theoretical prediction.     

Preparation of highly conductive reduced graphite oxide/poly(styrene-co-butyl acrylate) composites via miniemulsion polymerization

Polymer/reduced graphite oxide (rGO) composite nanoparticles with a high electrical conductivity were synthesized using the miniemulsion polymerization technique. The rGO was modified with a reactive surfactant, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), to facilitate monomer intercalation into the rGO nanogalleries. The AMPS-modified rGO was emulsified in the presence of styrene (St) and butyl acrylate (BA) monomers, and the stable miniemulsion was polymerized to form poly(St-co-BA)/rGO composite latex nanoparticles. The transition in the composite nanoparticles from an electrical insulator to an electrical conductor occurred at an rGO content of 10 wt% (relative to the monolayer content), yielding an electrical conductivity of 0.49 S/cm. The electrical conductivity of the composite nanoparticles reached 2.22 S/cm at 20 wt% rGO, yielding a much better conductivity than other polymer composites prepared using a GO filler. Importantly, the miniemulsion polymerization method for fabricating poly(St-co-BA)/rGO composite nanoparticles is easy, green, low-cost, and scalable, providing a universal route to the rational design and engineering of highly conductive polymer composites.     

Nanoencapsulation via interfacially confined reversible addition fragmentation transfer (RAFT) miniemulsion polymerization

Oligomer of styrene and maleic anhydride synthesized by bulk RAFT polymerization (SMA-RAFT) was used to construct a novel strategy for robust nanoencapsulation via interfacially confined controlled/living radical miniemulsion polymerization. After ammonolysis, SMA-RAFT becomes amphiphilic and can be used as a surfactant to prepare miniemulsion. The ammonolyzed SMA-RAFT molecules would self-assemble on the interface of water/droplets. This self-assembly property combining with the RAFT living polymerization chemistry demands the polymer chains to grow inwards gradually in particles, leading to the formation of a polymer shell. The hydrophilicity of ammonolyzed SMA-RAFT agent tuned by the ammonolyzed degree or structures of SMA-RAFT agent was found to play a key role in the final morphology. The well-defined nanocapsules with little solid particles can be obtained by using partially ammonolyzed SMA-RAFT with 0.5 wt% SDS as a co-surfactant.     

Synthesis, characterization, and energy transfer studies of dye-labeled poly(butyl methacrylate) latex particles prepared by miniemulsion polymerization

Poly(butyl methacrylate) (PBMA) latex particles have been copolymerized with new fluorescent naphthalimide dyes by miniemulsion polymerization. A new pair of naphthalimide dye monomers was synthesized and copolymerized with butyl methacrylate (BMA) via miniemulsion polymerization, producing approximately 80 nm diameter particles with a narrow size distribution. We were able to prepare polymers with molecular weights in excess of 100,000 g/mol. We also prepared 30,000 g/mol polymers using 1-dodecanethiol as a chain transfer agent. GPC and UV characterization suggest that nearly all of the dye monomers were incorporated into the PBMA polymer chains. The polymerized naphthalimide dyes can be used as a donor-acceptor pair for fluorescence resonance energy transfer (FRET) experiments. The analysis of FRET experiments is complicated by the slightly non-exponential decay of the donor naphthalimide dye. We propose a simple method to deal with this non-exponential behavior in the data analysis. Using our approach, we find that the Förster radius (R_o) between the donor and the acceptor dyes incorporated in the PBMA latex is 3.8 nm. This value is similar to the 3.6 nm Förster radius of a comparable model dye pair in ethyl acetate obtained by a different method.     

细乳液聚合制备改性硅溶胶／聚丙烯酸酯复合乳液

常温下一步法制备改性硅溶胶,并通过细乳液聚合制备改性硅溶胶／聚丙烯酸酯复合乳液。考查了温度对聚合速率和单体转化率的影响以及不同乳化剂含量下聚合过程中乳胶粒粒径的变化情况;测试了乳胶膜的吸水率,并用接触角法表征了乳胶膜的表面自由能。     

Reversible addition fragmentation transfer (RAFT) polymerization of styrene in a miniemulsion: A mechanistic investigation

The RAFT polymerization of styrene in miniemulsion using 1-phenylethyl phenyl-dithioacetate (PEPDTA) as a RAFT agent was investigated, in attempt to reveal the mechanism for the often observed inferior performance such as low polymerization rate, broad molecular weight distribution and particle size distribution in the RAFT miniemulsion polymerization with regular levels of surfactant and co-stabilizer (1 wt% sodium dodecyl sulfate and 2 wt% hexadecane). It is strongly evident that a few of large oligomer particles consisting of oligomer, RAFT agent (RAFT agent refers to the original RAFT agent), and monomer would be formed in the early stage of the polymerization due to the superswelling of the first nucleated droplets. With the regular levels of surfactant and co-stabilizer, the observed low polymerization rate, broadened molecular weight distribution, slow conversion of the RAFT agent, lower N_p, and broadened particle size distribution could be well explained by the formation of these large oligomer particles and their prolonged existence. When the formation of the oligomer particles was suppressed by increasing surfactant and co-stabilizer levels and wise selection of types of RAFT agent, the molecular weight distribution could be narrowed to around 1.3 and particle size distribution could be close to that of the conventional non-living miniemulsion polymerization.     

Synthesis and characterization of poly(ethyl methacrylate-co-methacrylic acid) magnetic particles via miniemulsion polymerization

Magnetic particles are very important systems with potential use in drug delivery systems, ferrofluids, and effluent treatment. In many situations, such as in biomedical applications, it is necessary to cover inorganic magnetic particles with an organic material, such as polymers. In this work, latices based on magnetite covered by poly(ethyl methacrylate-co-methacrylic acid) were obtained via miniemulsion polymerization. The resultant latices had particles in the nanometric range and presented a pronounced superparamagnetic behavior.